You should do a full Money Makeover and provide all the information necessary.
But UK mortgages are full recourse.
In other words, handing back the property does not cancel your obligations to the lender. If they sell the property for less than the mortgage, you owe the balance.
They are entitled to come after you in the Irish or UK courts for the balance. Whether they will or not is a different matter.
You should talk to your lender. They might agree to a voluntary sale and to write off the shortfall. They will get a lot less if you hand it back and they sell it.
Brendan